The Field of the Invention
The present invention refers to a composition adapted to facilitate the spinning of highly crimped cellulosic fibers, in particular of those produced with the viscose process, on machinery for cotton type fibers, and to a process for applying said composition on such cellulose fibers. The present invention further refers to the cellulosic fibers, in particular viscose and "Modal" spun fibers, treated with the said composition either in the production process or in the subsequent processing such as during application of a finish after dyeing or before the beating or carding stages.
It is known that many factors affect the workability of spun fibers, such as e.g. the morphology of its cross-section, the crimp, etc., but principaly its surface characteristics which are function of the application of the finish or are significantly influenced thereby. If an unsuitable finish is applied to the fibers neps are formed, filaments are broken, electrical charges are formed in the card; successively the card web and/or the bench slivers generally have a strong friction and slide with difficulty. The inverse may also be true, again due to the use of unsuitable finishes, whereby insufficient cohesion occurs and consequently fibers may fly off, winding on rolls, and other drawbacks may occur.
In particular the highly crimped fibers, both of the normal viscose type and of high tenacity and "Modal" (according to the ISO norms) type are considerably difficult to spin as pure and as blended fibers. The presence of numerous convolutions makes it very difficult to balance the friction between the fiber and the machine components and between the fibers themselves, with respect to the break tenacity thereof and to the requirement for good slideability of the semi-finished products like card web, draft ribbons, bench slivers in the cotton type transformation cycle.
To avoid the aforesaid drawbacks, the cellulosic fibers, and in particular viscose spun fiber, must be treated in the phase of the fiber production or before carding or after dyeing, with one or more substances which permit regular processing. These substances are notoriously applied in the form of solutions or fine aqueous emulsion, by spraying, dripping, bath immersion, etc., and consist of: mineral oils, oleines, surfactants, etc.
They have mainly the functions of:
imparting cohesion to the ribbon and the yarn,
permitting an appropriate sliding of fiber on fiber,
imparting to the yarn a low fiber-metal friction,
preventing the accumulation of electrical charges on the fibers
and on the other hand these substances:
must not produce disagreeable odors, and
should be adapted to be purged and be compatible with the dyes.
The substances used up to now as finishes proved unsuitable to perform all the functions set forth above and the higher the degree of crimp of fibers the less they proved efficient.